The present invention relates to circular knitting machines and to methods for knitting fabrics on circular knitting machines. In particular, the present invention relates to coordinating the selective reciprocation of the needles and sinkers to counteract xe2x80x9crobbing backxe2x80x9d of a lay-in yarn.
Circular knitting machines are widely used to produce knitted fabric, such as knitted fabric that is tubular. A conventional circular knitting machine includes a vertically extending cylinder, and multiple sinkers and latch needles that extend around and move relative to the upper end of the cylinder. The sinkers reciprocate radially and the latch needles reciprocate vertically in a cooperative fashion to produce knitted fabric.
Circular knitting machines are used to make many types of fabric, including jersey and fleece fabrics. For example, prior fleece fabrics of the type used in sweatshirts have floating portions of lay-in yarn extending above the xe2x80x9cfacexe2x80x9d of the base fabric structure. Knitted fleece fabrics are usually grouped in the categories of three-end fleeces and two-end fleeces.
It is known to knit three-end fleeces on a circular knitting machine specifically designed to produced this type of fabric. In these machines, two yarns are knitted and one is laid in, and the sinkers are typically double-nosed. The double nosed sinkers are used individually to allow for more lay-in yarn to be measured in. However, these machines are specialized machines that are not readily transformable from standard raceway machines.
In contrast, it is known to knit two-end fleeces on circular knitting machines with standard raceways. Two-end fleeces are typically produced by the use of single-nosed sinkers. In this instance, the length of the lay-in yarn may be measured by drawing the respective needle below the sinker knitting platform, sometimes in combination with the sinker throat pushing the lay-in yarn around the needle shaft. Two-end fleeces formed in this manner are generally used for less expensive sweatshirt-styled fabrics. Whereas it is conventional to use a basic single-knit raceway machine having single throat sinkers to produce fleece fabrics, there is a limitation as to the amount of lay-in yarn that can be introduced. Typically, the amount of land or flat in the stitch cam associated with a lay-in feed is not sufficient to counteract severe robbing back of the amount of lay-in yarn being fed. Likewise, even though lowering the stitch cam on a standard raceway, two-end fleece machine increases the amount of lay-in yarn incorporated into the fabric, it is common for the stitch cam to be lowered as far as possible in an effort to maximize the amount of lay-in yarn incorporated into the fabric. This can jeopardize the quality of the fabric, because unwanted holes in the fabric can be formed by breaking the yarn of the previous stitch not knitted off by the tucking needle. Likewise, the welt cams on the lay-in feeds can also rupture stitches if the welt cams are attached to the same stitch cam post that holds the tuck cam (as is normal), and that post is adjusted for a deep draw for the tuck cam.
In the past, special machines for manufacturing two-end fleece have been built by Vanguard Supreme Knitting Machine Company, a division of Monarch Knitting Machine Corp. These special machines introduce lay-in yarn with a double nosed sinker, and the amount of lay-in yarn is respectively measured by the distance that the upper throats of the sinkers push the lay-in yarn around the needle shanks. However, these machines, like three-end fleece machines, are specialized machines that are not readily transformable from standard raceway knitting machines.
Accordingly, there is a need for methods and apparatus that provide improved countermeasures against robbing back, such as for standard raceway knitting machines, so that high quality fleece fabric can be produced on standard raceway knitting machines.
In accordance with one aspect, the present invention relates to a method and apparatus for producing a knitted fabric having a lay-in yarn, and more specifically the invention relates to a modification that may be incorporated with minimal added expense into both existing and new raceway-type knitting machines, so that they can produce fabric having the desired lay-in yarn feature.
In accordance with one aspect of the present invention, a circular knitting machine includes multiple needles arranged for reciprocating in the direction of the axis of the machine, and needle cam tracks arranged around the axis for respectively engaging butts of the needles so that one or more intervening needles of the needles are positioned between at least a pair of the needles, with the intervening needle(s) preferably including all of the needles positioned between the pair of needles. During a predetermined period, the pair of needles engage and draw down a lay-in yarn and hold portions of the lay-in yarn in a lower position, and the intervening needle(s) do not draw down the lay-in yarn. Preferably the intervening needle(s) are substantially maintained in a welt position and do not substantially interact with the lay-in yarn during the predetermined period.
The knitting machine also includes multiple sinkers arranged for moving radially relative to the axis, and at least one sinker cam track arranged around the axis for selectively engaging and moving the sinkers. The sinkers are moved so that during the predetermined period, there are one or more intervening sinkers of the sinkers that are positioned between the pair of needles and arranged in a forward position. As a result, the section of the lay-in yarn that spans between the pair of needles is retained over the nib(s) of the intervening sinker(s) positioned between the pair of needles. Preferably the section of the lay-in yarn that spans between the pair of needles is contemporaneously retained over all of the nib(s) of the intervening sinker(s) positioned between the pair of needles. This advantageously counteracts robbing back of the lay-in yarn.
In accordance with one aspect of the present invention, a set of cam tracks for a circular knitting machine is provided, and preferably the cam tracks can be used in standard raceway knitting machines so that these machines can advantageously produce a high quality fleece fabric. In accordance with this aspect, the set includes multiple needle cam tracks that provide the above-described arrangement and operation of the needles, and at least one sinker cam track for moving the sinkers as described above. Preferably each of the cam tracks includes multiple cams that are capable of being removably mounted to the knitting machine.
In accordance with one aspect of the present invention, the multiple needle cam tracks include a first needle cam track for engaging the butts of the pair of needles for controlling the pair of needles during the predetermined period, and a second needle cam track for engaging the butts of the intervening needle(s) for controlling the intervening needle(s) during the predetermined period.
In accordance with one aspect of the present invention, a method of knitting a fleece fabric is provided. In accordance with this aspect, a lay-in yarn and a jersey yarn are introduced into a circular knitting machine. A base fabric structure is formed from the jersey yarn by operating at least some of the needles and sinkers of the machine. In addition, the lay-in yarn is connected to the base fabric structure so that floating portions of the lay-in yarn extend above a face of the base fabric structure. The floats (i.e., floating portions of the lay-in yarn) are formed by operating the above-discussed pair of needles to engage, draw down, and hold portions of the lay-in yarn in a lower position during the predetermined period. At the same time, the above-discussed intervening needle(s) are preferably substantially maintained in a welt position such that the intervening needle(s) do not substantially interact with the lay-in yarn during the predetermined period. In addition, the above-discussed intervening sinker(s) are arranged in a forward position during the predetermined period, so that the section of the lay-in yarn that spans between the pair of needles is retained over the nib(s) of the intervening sinker(s). Preferably the section of the lay-in yarn that spans between the pair of needles is contemporaneously retained over all of the nibs of the intervening sinkers. This advantageously at least partially counteracts robbing back of the lay-in yarn.